1. Technical Field
The present invention relates to an equivalent circuit model of a multilayer chip capacitor (or condenser) and a circuit constant analysis method, program, device, and circuit simulator therein and relates to an improvement in the equivalent circuit model of the multilayer chip capacitor and the circuit constant analysis method, program, device, and circuit simulator therein that is preferred in characteristics simulation of the circuit which includes, for example, a multilayer chip capacitor that uses ceramics.
2. Background Art
Multilayer chip capacitors, and multilayer ceramic capacitors (MLCCs) in particular are widely used in electronic devices such as cellular telephones. These capacitors include a right-angled parallelepiped shape dielectric chip and a plurality of internal electrodes, each of which, along with being embedded in the above-stated chip, has one terminal pulled to the surface of the aforementioned chip as well as an external electrode formed on the surface of the aforementioned chip so as to make electric contact with the terminals of the aforementioned internal electrodes. The design and analysis of a circuit that utilizes a multilayer chip capacitor employs Simulation Program with Integrated Circuit Emphasis known as SPICE—an open source analogue electronic circuit simulator, for example, and as an equivalent circuit therefor, an ideal capacitor and/or a simple RLC series circuit shown in FIG. 1(A) are utilized. Due to the presence of parasitic components, however, it is impossible to represent the characteristics of the multilayer chip capacitor sufficiently in an ideal capacitor model. Moreover, when the RLC series circuit shown in FIG. 1(A) is used, since each of circuit elements is frequency dependent in actuality, significant errors would result, and the actual performance of the circuit designed this way would be quite different from the design target. Accordingly, various equivalent circuit models have been proposed for conducting more accurate simulation.
Patent Documents 1 through 3 below are herewith disclosed as background art related to equivalent circuit models for capacitors. Patent Document 1 is aimed at deriving an equivalent circuit model for a capacitor in time domain by a procedure that can be used regardless of types of capacitors. It first forms one of the RC, RL, and RCL circuits as an equivalent circuit model for the frequency characteristics the user input, and calculates evaluation functions to determine the accuracy of the model. The circuit constants are determined by minimizing the values of the evaluation functions.
In Patent Document 2, an equivalent circuit is structured such that the real part of the impedance of the equivalent circuit changes with the frequency of an applied AC signal in near conformity with the real part of the measured impedance of the actual circuit. Specifically, the proposed equivalent circuit includes a first circuit for a storage part and a second circuit for a terminal, which is connected in serious to the first circuit, wherein the first circuit includes at least one series circuit in which a first parallel circuit and a second parallel circuit are connected in series, and wherein the first parallel circuit includes a first resistance and a first inductance connected to the first resistance in parallel, and the second parallel circuit includes a second resistor and a capacitance connected in parallel to the second resistance. Patent Document 3 resembles the above-described Patent Document 2, and discloses an equivalent circuit model in which a series circuit of a resistance and a capacitance is additionally provided.
Furthermore, in Non-Patent Document 1 listed below, a circuit modeling technique is disclosed in which a fractional polynomial is factorized at every second order when performing the modeling of circuit elements, and a parallel connection of series resonance circuits or a series connection of parallel resonance circuits is utilized.